Process model of plasma enamelling

A computational model has been developed to simulate the deposition of enamel on steel substrates by the use of plasma spraying. The model predicts the temperature profiles of the feedstock particles during their flight in the gas jet and the concurrent heating of the substrate. A process window is predicted for enamel deposition in terms of plasma gas composition and feedstock particle size. The model also predicts that the plasma jet produces a thermal shock at the surface of the coating and a high temperature gradient through its thickness during the scanning action. A series of experimental trials confirmed that plasma spraying could successfully produce dense coatings on steel. An inherent advantage of the process is that the enamel feedstock powder is fused separately in the plasma while the substrate remains at a low temperature. This enables enamelling to be carried out in a single stage operation without the need for a furnace, which offers the potential of widening the applicability of enamel coatings.